Most all baits that you purchase from a location has all of the info printed on the package, some are not clearly marked, those are the ones I generally like to shy away from.

If you are looking at buying used, then the only way to know for sure is to weigh them, that is if you are not familure with them, as you get more and more experience with baits you will be able to know what you are looking at.

You can help yourself by going to the local store and just take your time and look at different baits that you are interested in, the info on the boxes will help you with getting familure with various shapes and sizes of tackle and what their purpose is.